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.ing to the composition of the material bein treated. A floating siph i to regulate the amount of acid and water sup- UNTTED, S'rnrns f;

arnur arse NATHANIEL A. PRATT, or ousutnsrou, scorn oxuomun, AND unoues T. LEWIS, OFPHILADELPHILA, PENNSYLVANIA.

nuruo'v'tmsur nu .rssn'raue success-r ic aces, as.

Specification forming part of Letters Patent N 1728,7523, dated July 9, 1875;. i

To all whom it may concern.-

.Be it known that we, NATHANIEL ALPHEUS PRATT, of Charleston, South Carolina, and

GEORGE T. LEWIS, of Philadelphia, Pennsylvania, have invented a new ,and useful Improved Method in Treating Phosphatic Rock or other r phosphatic substances or other material, to make super-phosphate of lime or manure and other commercial phosphates; and

we'do hereby declare the following to be a full, clear, and exact description thereof.

Our process is adapted especially to the treatment of the native phosphates of South Carolina, other phosphatic material, but may be also used in other kindred applications. It consists in grinding the phosphatic materials-say ten.(10)tons-in an e or chaser, or other well-known form of mill; andwhile this is going on a gradual stream of dilute acid is fed into the mill of suflicient strength and quantity to dissolve ordecom pose the phosphate or other material, and having sufiicient water with it to form with the resulting mass a paste. Forthis purpose there will berequired a mixture'of sulphuric acidfive to five and a half tons, more or less-of strength 66 Baum, and of water, either fresh or salt, ten to fifteen tons, more or less, accord on may be employed plied to the mill according to the amount of material ground in a given time. Instead of sulphuric acid anyother acid oracid-salt may be employed. The 1 mixed, paste produced is 'P to be placed in ordinary baggiugzsacks orsgch other parcel as may be 'found most fllhieht, and submitted to hydraulic or other pressure until the phosphoric extract is squeezed out. Pressure in a centrifugal machir will answer well. The phosphatic extract thus pressed out may J dried with artificial be evaporated by artificial heat or driers, such as lime, plas ter of Paris, sawdust, cotton-seed, or oilcalie. Dried phosphates or super-phosphates maybe used, and the compound packed for manure; or, after it is thus dried, and in- United States of. America, or any ordinary burr-stone mill stead of mixing it with the substances lest named,-carbonate of soda, (soda ash,) carbonate oi potash, (potash of commerce,) sulphate of ammonia, sulphate of soda, chloride of sodium, (common salt,) carbonate of magnesia or other salts or alkaline earths may be mixe in a dry state; or, instead of evaporating the phosphatic extract, as in the first instance, a mixture therewith of the alkaline salts above mentioned, or the alkaline earthic bases may be calcined or dried.

What we claim, and desire to secure by Letters Patent of the United States, its-- after the scribed, by evaporating down to dryness orxto a crystallizable state to make a nuanureol other commercial product.

2. Treating the phosphatic extract obtained after the pressure or squeezing, as herein described, bymixing the same with the salts of soda, potash, magnesia, or ammonia, or with the bases of said salts, and then evaporating the mixture to make a manure or other commercial product.

, 3. Treating, in a reverberatory or calcining furnace, the phosphatic extract obtained after the pressure or squeezing, after evaporation,

g 'as herein described, mixed with the saltsof soda, potash, ammonia, or magnesia, to produce compound phosphates of lime and of the alkalies.

4.. Mixing the phosphatio extract obtained after pressure or squeezing with plaster of aris, lime, starch, sawdust, cottonmeedmil ,ca adrie rho p e u the purpose-trashin a manure or other commercial product. V N. A. PRATT.

GEORGE T. LEWIS.

Witnesses-to signature of N. AaPRhTT:

R. S. Bnuus, R. M. HAnDoN.

Witnesses to signature of GEORGE T. LEWIS:

EDWARDJ. FASY,

. SAM. N. LEWIS.

be made, and after mixture the compound may 1. Treatingthe phosphatic extract obtained pressure or squeezing, as herein dec eeper-Rhom for 

